In AMPSetup > General page>Historical Retention section we have Delete inactive SSID option. Airwave will retain the SSID information based on this value. If it is set to less than 30 days and SSID is inactive, Airwave will purge the SSID information.
We could also filter the clients based on SSIDs, create a custom filter in clients>connected page and click on client which will take you to clients>Details page which will proivde details of client association.
If my post address your query, give kudos:)